DE 10 2012 020 431 A1 discloses a filter device comprising at least one filter element, through which a fluid to be purified can flow with a determinable fluid operating pressure and which can be accommodated in a housing. The fluid pressure prevailing at the respective filter element may exhibit general pressure increases or pressure peaks damaging to the respective filter element, in particular to the filter material thereof. The pressure increases or peaks can be reduced and/or smoothened by a compensation device that acts directly upon the respective filter element and that has at least one flexible compensation element that enables the volume of the fluid chamber of the housing to be increased in accordance with a pressure peak or pressure increase. In the prior art solution, the flexible compensating element is arranged upstream between the outside of the filter material of the filter element and the adjacent inner wall of the housing, i.e. the fluid passage between the compensating element and the filter element is connected to the fluid inlet and the fluid supply is thus arranged upstream. The fluid filtered by the filter element is discharged from the filter device downstream via a centrally arranged opening in the end cap.
In the prior art solution, the flexible compensating element is configured in the nature of a bowl inserted in the housing of the filter device and is preferably made of a cellular rubber material. The prior art solution can also be used to compensate for the increase in volume of a freezing aqueous urea solution (as used in SCR exhaust systems, particularly in automotive engineering) via the cellular rubber compensating element in order to help prevent damaging pressure influences exerted on the sensitive filter element material by the increase in volume.
The volume increase could lead to the inoperability of the filter device, in particular if the freezing of the fluid material results in a tear or the like in the filter element material. Because of the relatively rigid material properties of the cellular rubber used for the compensating element, the compensating mechanism of the prior art filter device, acting as a pulsation damper, is suitable for smoothing out or attenuating sudden pressure spikes, but is hardly suitable for compensating the increase in volume that occurs in the filtering of aqueous urea solutions in the event of freezing.